Apparatus for metallically coating phonograph records



April 17, 1934. A. G. RUSSELL 1,954,950

APPARATUS FOR METALLICALLY coA'TiNG PHONOGRAPH RECORDS":

" Originl Filed May 29, 1931 IN VE/VTOL'? A. GRUSSELL v Patented Apr. 17,1934

UNITED STATES APPARATUS FOR PATENT OFFICE METALLICALLY COATING PHONOGRAPH RECORDS Application May 29, 1931, Serial No. 540,866 Renewed January 1'7, 1934 5 Claims. (Cl. ill-12.2)

This invention relates to apparatus for metallically coating phonograph records and particularly to such devices utilizing the sputtering effect upon a cathode in a glow discharge chamber.

For a number of years attempts have been made in the commercial production of phonograph records to prepare the records for electroplating by coating them with a conducting material such as gold by means of the sputtering process. This process consists essentially of placing the wax master record between two electrodes in an evacuated chamber and impressing a suitable potential diiference across the electrodes such that a glow discharge takes place. The surface of the cathode is thus sputtered and the fine particles loosened from the cathode deposited in a film of metal on the wax master. The heat of the discharge, however, has been found to cause the wax master to become plastic if sputtered continuously at a high rate, and to obviate this difficulty the sputtering had to be done either intermittently or at a greatly reduced rate to maintain its temperature at a safe level. These methods are unsatisfactory from the standpoint of time consumed and quality of coating obtained.

The object of the present invention is to improve the sputtering apparatus so that the time required to deposit a suitable metallic coating upon a phonograph record therewith will be materially reduced and the coating itself substantially improved in quality.

In carrying out this object, a cooling means as hereinafter described is provided within the sputtering device to maintain the temperature of the phonograph record to be coated at a suitable level. This makes possible at oncea high speed continuous sputtering apparatus to reduce the time required to deposit a coating, and a more homo geneous and, therefore, better quality coating.

To illustrate a preferred embodiment of my invention reference is made to the accompanying drawing wherein:

Fig. 1 is a wax record particularly adapted to be cooled without danger of cracking and therefore well suited for use in a sputtering device. It is comprised of a thermo-conductive disc 10 having one surface slightly recessed and covered with a thin layer of recording wax 11;

Fig. 2 shows a wax record in place in the sputtering device together with the details of the latter;

Fig. 3 is a sectioned side elevation of the device showing a possible source of electrical energy. This is comprised of a transformer 30 connected across a 110 VA. C. line and wound to furnish electrodes is dependent upon the amount of gas remaining within.

Referring now to Figs. 2 and 3, the device is comprised essentially of a cylindrical metal shell 12 open at the top, with the edge ground perfectly fiat to make an air tight joint with a thick glass cover 13. The side of the shell is slotted and covered with a glass plate to form a window 2'7 through which the discharge may be observed. A mercury vapor pump 14 and an'oil pump 15 working in series are used to evacuate the chain'- ber, while a leak valve 16 in the line 17 leading to the chamber serves to regulate the degree of evacuation. The vacuum lead 35 is centrally located to equalize the flow effects of the air as it is being drawn out. 4

At the bottom of the shell is a horizontal glass plate 18 supported by three rubber legs 19 and covered with a thin sheet of gold 20, or other sputterable material, which constitutes the cathode of the device. The anode is an aluminum disc 21 secured to the top, parallel to the cathode and as far away from the latter as is expedient. The rod 22 fastening the anode to the top extends through the top and serves as a lead for an electrical connection.

The thermo-conductive disc 10 is supported in an inverted position over the cathode and secured to the cooling plate 23 which, in the present device, is about 3" from the cathode. The inverted position prevents any undesirable materialsuspended in the air, or loosened from the top of the shell, from falling on the wax layer 11 and introducing minute irregularities in the surface of the coating to result later in the production of noise in the finished record. The means used to fasten the record to the cooling plate may be any suitable holding device such as a number of clamps around the periphery of the metal back. The spacing between the record and cathode should be uniform to secure an even coating of the fold. The relation between the degree of evacuation, potential across the electrodes and spacing of the electrodes and plate should be. such that the dark spaceaccompanying the discharge is located of the distance from the cathode to the plate away from the cathode. It has been found that the sputtering is most effective at this position of the dark space.

The cooling plate 23 is a metal disc thick to which is secured a flat coil of pipe 24 having an intake and outlet at 25 and 26 respectively. The pipe is made continuous so that there are no joints within the shell. This is desirable from a structural standpoint since the pressure within the shell is brought considerablybelow atmospheric and an internal pressure upon any joint within the shell might cause the joint to leak. At the pressure and temperature conditions found in the shell, water is instantly vaporized and an influx of vapor would greatly disturb the required vacuum and render the apparatus unsteady or even inoperative.

The leads 25 and 26 together with the brace 28 comprise the means for suspending the coil from the top. The suspension should be rigid to insure air tight joints between the support and top. The intake is connected to a source of water supply through a valve 29.whi1e the outlet 26 may be disposed of in any convenient manner.

Having described the various elements of my may be provided for the top to facilitate this proloo'se material.

minute hollows in the deposited master and corcedure. Next, a wax record to be coated is placed on the plate and secured to it. The record must be thoroughly cleaned before it is put in place to insure the absence of wax cuttings and other This if left in the grooves forms responding excrescences in the record which produce objectionable clicks in the sound reproduced therefrom. After the record is secure, the

cover is replaced and water sent through the cool-' ing coils. The cooling is done very slowly to avoid a sudden change of temperature within the wax. The temperature may be as low as desired, but it must be evenly distributed to prevent cracking of the record.

- The oil and mercury pumps are started and the chamber is evacuated to a pressure of about 0.001 millimeters of mercury. At this point the potential is impressed across the electrodes .and a glow discharge effected. The evacuation is continued until the pressure is such that the dark space is about 1' from the cathode which, in the present machine, corresponds to of the distance, from the cathode to the plate. The pressure is then maintained at this level throughout the sputtering by the leak valve.

. The sputtering is continued for about ten minutes which has been found to be sufficient for plating purposes. At the end of ten minutes air is admitted into the chamber, the cooling water is shut oil and the wax is brought slowly to room temperature. The top is then removed and the record taken from the cooling plate ready for plating in the copper plating bath.

It is understood that various changes, can be made in the structure shown without departing from the spirit of the invention and the scope of the invention, therefore, is not to be limited by the foregoing illustrative description-but is to be determined by the appended claims.

What is claimed is:

1. Apparatus for sputtering phonograph records comprising an evacuated hollow cylinder and a removable top therefor, means for maintaining the evacuation at a predetermined state, a gold cathode at the bottom of the cylinder, an anode near the removable top and secured to it, a source of electrical energy for the cathode and anode, means for suspending a record from the removable top in an inverted position and parallel to the cathode, said means comprising a metal platen secured to a coil of pipe integral with the top and. containing a cold fluid for conducting inder and a removable top therefor, a mercury vapor pump and an oil pump to maintain the state of evacuation, an airlead centrally located to equalize the'fiow efiects of the air, a gold cathode at the bottom of the cylinder, an anode near'the removable top and secured to it, a source or electrical energy for the cathode and anode, means for suspending a record from the removable top in an inverted position and parallel to the cathode, said means comprising a metal platen secured to a coil of 'pipe integral with the top and containing a controllable stream of cold water for conducting away the excess heat generated by the sputtering process.

3. Apparatus for sputtering thermo-critical articles comprising an evacuated apertured container, a removablev cover for the aperture, means for maintaining the evacuation at a predetermined state, a cathode of sputterable metal within the chamber, an anode secured to the cover, a source of electrical energy connecting the anode and cathode, a removable cooling system within the chamber, and means on the cooling system for supporting the thermocritical articles whereby the heat in said articles is conducted away and the articles thereby maintained at a safe working temperature.

4. In a continuous sputtering apparatus for'a thermo-critical structurally weak phonograph record, a stifl. thermo-conductive support for the record, said record being secured to said support, a cooling system within the apparatus coextensive with the surface of the record, and means for securing said thermo-conductive support to the cooling system whereby heat is conducted rapidly from the record to maintain it at a safe working temperature.

5. In a continuous sputtering apparatus for a thin wax phonograph record, a cooling plate within the apparatus for the thin wax record. a stiff 

